Control for crane hoist having a lift ram

ABSTRACT

Device of the invention comprises a limit switch arrangement for positively controlling the upward travel of the lift ram of a crane hoist. The arrangement includes a pivotally mounted sensing arm extending into the path of the ram and connected by means of a cable with the counterweighted actuating arm of the limit switch in the electrical circuit powering the ram-lifting mechanism of the crane hoist. A pivotally mounted elongated counterweight is connected with the intermediate portion of the cable by means of a fitting through which the cable is threaded. The counterweight normally functions to maintain the sensing arm in initial resting position and the actuating arm of the limit switch in position keeping the limit switch closed and current flowing to the ram-lifting mechanism. Means are provided on the cable between the counterweight and the actuating arm to limit movement of the cable through the fitting. In operation, lifting of the sensing arm by the top of the ram as it rises causes lifting of the counterweight and removal of cable-tension from the counterweighted actuating arm so that it may rotate to position causing the limit switch to open and interrupt flow of current to the ram raising mechanism.

United States Patent [191 Nanowsky 1 Sept. 10, 1974 CONTROL FOR CRANE HOIST HAVING A LIFT RAM Inventor: John P. Nanowsky, Boardman Township, Mahoning County, Ohio [73] Assignee: United States Steel Corporation,

Pittsburgh, Pa.

Filed: Sept. 27, 1973 Appl. No.: 401,315

References Cited UNITED STATES PATENTS 9/1924 Lammers 254/173 R 3,265,360 8/1966 Tax 212/132 X 3,310,291 3/1967 Wiggins 254/173 R FOREIGN PATENTS OR APPLICATIONS 751,703 7/1949 Germany 212/132 Primary ExaminerRobert B. Reeves Assistant Examiner-Joseph J. Rolla Attorney, Agent, or Firm-Walter P. Wood [5 7] ABSTRACT Device of the invention comprises a limit switch atrangement for positively controlling the upward travel of the lift ram of a crane hoist. The arrangement includes a pivotally mounted sensing arm extending into the path of the ram and connected by means of a cable with the counterweighted actuating arm of the limit switch in the electrical circuit powering the ramlifting mechanism of the crane hoist. A pivotally mounted elongated counterweight is connected with the intermediate portion of the cable by means of a fitting through which the cable is threaded. The counterweight normally functions to maintain the sensing arm in initial resting position and the actuating arm of the limit switch in position keeping the limit switch closed and current flowing to the ram-lifting mechanism. Means are provided on the cable between the counterweight and the actuating arm to limit movement of the cable through the fitting. In operation, lifting of the sensing arm by the top of the ram as it rises causes lifting of the counterweight and removal of cable-tension from the counterweighted actuating arm so that it may rotate to position causing the limit switch to open and interrupt flow of current to the ram raising mechanism.

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CONTROL FOR CRANE IIOIST HAVING A LIFT RAM The present invention relates to control apparatus and more particularly to a control for a crane hoist having a lift ram.

The subject invention finds particularly advantageous utilization on an E.O.T. soaking pit crane in a steel mill and in that use it will be described.

Where sufficient headroom between the soaking pit crane and the roof trusses of the soaking pit building is available, a conventional arrangement whereby a sensing arm projecting into the path of a vertically traveling lift ram of the soaking pit crane is connected with the counterweighted actuating arm of a superposed limit switch can be utilized to control the upward movement of the ram. With this arrangement the sensing arm contacts the leading end of the vertically rising ram and relieves the actuating arm of the limit switch so that the latter rotates to a position wherein the limit switch is opened and current to the electrically powered ramlifting mechanism is cut off. Where sufficient headroom exists, this arrangement can be used since the limit switch can be positioned high enough so that it is above the end of the path of travel of the upwardly moving ram including overtravel thereof after the current has been interrupted by the limit switch.

Prior to my invention, when adequate headroom was not available, the ram was provided with a shelf projecting from its side at a distance below its leading end, and a guided counterweight was suspended by a cable from the switch arm in the path of the shelf. With this arrangement, as the counterweight was raised by the shelf, the switch arm rotated to the off position and current to the ram-lifting mechanism was cut off. This latter arrangement had several disadvantages, the most detrimental of which was the fact that it was not failsafe. For example, lateral movement of the upwardly rising ram frequently caused the shelf projecting from the ram to miss engaging the counterweight so that the current to the lifting mechanism was not cut off. This frequently caused the ram to be projected through the roof of the building with consequent serious safety hazards. Also, by-passing of the counterweight by the shelf frequently resulted in the shelf destroying the counterweight guides and the limit switch itself.

Accordingly, it is the primary object of my invention toprovide a fail-safe control apparatus for the lift ram of a crane hoist which can be utilized in areas where headroom above the crane hoist is limited.

It is a more specialized object of my invention to provide a control device as set forth above which includes a sensing arm pivotally mounted on a support stand and projecting therefrom into the path of travel of the hoist ram; a limit switch-having a counterweighted actuating arm disposed on the support stand above the sensing arm and connected with the sensing arm by means of a cable; an elongated counterweight pivotally mounted on the support stand below the sensing arm and having a fitting pivotally mounted thereon for receiving the intermediate portion of the cable connecting the sensing arm and the limit switch actuating arm; and a sleeve fixed on the cable between the actuating arm and the fitting normally abutting the fitting and limiting travel of the cable therethrough in one direction.

These and other objects will become more apparent after referring to the following specification and drawing in which:

FIG. 1 is a schematic elevational view of a soaking pit crane hoist equipped with thedevice of the invention;

FIG. 2 is a plan view of the device of the invention;

FIG. 3 is an elevational view of the invention;

FIG. 4 is an elevational view taken substantially along the lines IVIV of FIG. 3; and

FIG. 5 is a schematicdiagram of the operation of the invention.

Referring more particularly to the drawing, reference numeral 2 designates generally a soaking pit crane hoist having a lift hoist column or ram 4. An ingotmanipulating mechanism 6 is suspended from the bottom of the ram 4 in conventional manner. The ram 4 is normally disposed in a ram cage 8 when it is in raised inoperative position as shown in solid lines in FIG. 1. The ram is raised and lowered from its operating position as shown by broken lines in FIG. 1 by conventional electrically powered drum-and-cable means 10.

The device of the invention, designated generally by reference numeral 12, is mounted on the upper platform 14 of the crane hoist 2 below the roof 15 of the soaking pit building, as best shown in FIG. 1. An upstanding support 16 is disposed adjacent one side of the ram cage 8. A beam 18 made up of a pair of angle members is upstanding between the support stand 16 and the cage 8 and is provided with a series of vertically spaced holes 20 therealong for a purpose which will become apparent.

A power limit switch 22 having an actuating arm 24 with a counterweight 26 on one end is mounted on the top of the support stand 16 with the end of the arm 24 remote from the counterweight extending toward the vertical path of the ram 4. The actuating arm 24 is constantly urged by the counterweight 26 to a position opening the limit switch 22 which is connected with the electrically powered ram-lifting mechanism. Stops 28 are provided one at each end of the arcuate path of travel of the actuating arm 24.

A sensing arm 30 is pivotally mounted by one end 34 on the support stand 16 and normally extends therefrom into the path of travel of the ram 4. As best shown in FIG. 4, the sensing arm 30 is below and laterallyoffset from the limit switch 22 and actuating arm 24. The sensing arm is adjustably fixed in desired position by means of a pin 36 which fits into one of the holes 20 in the beam 18.

An elongated counterweight 38 is pivotally mounted by one end 40 to the support stand 16 spaced below the sensing arm 30. A stop pad 41 adapted to receive the counterweight 38 when it is in lowered position is provided on the platform 14 of the crane 2. A fitting 42,

which may be in the form of an arcuate tube, is pivotally mounted by means of a pivot shaft 44 on the upper portion of the counterweight 38 adjacent the end thereof remote from its pivoted end 40 substantially normal to the longitudinal axis of the counterweight38.

As best shown in FIGS. 3 and 4, a cable 46 is attached by one end to the sensing arm 30 and by its opposite end to the end of the actuating arm 24 remote from the counterweight 26. The ends of the cables are attached to the sensing arm and the actuating arm by conventional means. The intermediate portion of the cable 46 is threaded through the fitting 42, as best shown in FIG. 4. A collar 48 is fixedly attached to the cable 46 between the actuating arm 24 and the fitting 42 and normally, as best shown in FIG. 4, abuts a washer 50 which is disposed against the end of the fitting 42. The outside diameter of the collar 48 is such that it cannot pass through the washer. The collar 48 limits movement of the cable 46 in one direction through the fitting 42.

In FIGS. 3 and 5, the sensing arm 30 is shown in a horizontal initial position. The counterweight 38 is parallel with and moves parallel with the sensing arm 30 and forms a parallelogram therewith by virtue of the cable 46.

In operation, when the leading end of the ram traveling upwardly engages the projecting end of the sensing arm 30, the arm 30 is moved upwardly to tripping position as shown by broken lines in FIGS. 3 and 5. Upward movement of the arm 30 raises the end of the counterweight 38 remote from its pivoted end so the counterweight 38 remains parallel with the sensing arm 30. When the sensing arm 30 and the counterweight 38 are thus raised, cable-tension is removed from the actuating arm 24 of the limit switch 22 so that the actuating arm rotates by virtue of the counterweight 26 from the operating position shown by solid lines in FIGS. 3 and S to the switch tripping'position shown by broken lines in FIGS. 3 and 5. This movement causes the limit switch to open and cut the current to the ram-lifting mechanism. This discontinues powered vertical lifting of the ram although the ram overtravels a certain distance after the current has been cut off. Such overtravel is controlled by conventional mechanical and electrical brakes (not shown).

If it is desired to stop power lifting of the ram earlier, the sensing arm 30 may be moved to a lower initial position by resetting the pin 36 in a lower hole along the beam 18. If it is desired to have the ram travel to a higher level before power lifting is stopped, the sensing arm is adjusted to a higher initial position by fitting the pin 36 in a hole at a higher elevation along the beam 18.

An important feature of the device of the invention is that it is fail-safe since breakage of the cable 46 be tween the counterweight 38 and the sensing arm 30 would instantly remove cable-tension from the actuating arm 24 and cause the electrical current to the ramlifting mechanism to be interrupted by the limit switch. Similarly, breakage of the cable between the actuating arm and the counterweight 38 would also cause the actuating arm 24 to rotate under the force of counterweight 26 to tripping position opening the limit switch and interrupting the current to the ram-lifting mechanism. Although I have shown the fitting 42 in the form of an arcuate tube, it will be understood that the fitting may be made in other forms, such as a short straight tube, an eyelet, or the like, for circumferentially engaging the cable 46 and securing it to the counterweight 38. The fitting 42 is pivotally mounted on the counterweight 38 so that the portions of the cable connected with the sensing arm 30 and the actuating arm 24 will be properly aligned no matter what the positions of the sensing arm 30 and the counterweight 38 are when the sensing arm is lifted by the leading end of the rising ram. The limit switch 22 may be obtained on the market and may be of the type manufactured by Square D Company, Milwaukee, Wisconsin, labeled Youngstown Power Limit Switch-Catalog No. DG30.

While I have shown but one embodiment of my invention, other adaptations and modifications may be made without departing from the scope of the following claims.

I claim:

1. In a crane hoist having a ram disposed for movement in a vertical path, electrically powered means for raising said ram, a limit switch connected with said means for controlling the flow of electrical current thereto, an actuating arm connected with said limit switch, said actuating arm being counterweighted to constantly urge said limit switch into currentinterrupting position, the improvement therewith of apparatus for controlling the upward movement of said ram through actuation of said limit switch, said apparatus comprising a support stand disposed adjacent the path of said ram, said limit switch being disposed on said support stand, a sensing arm pivotally mounted by one end on said support stand spaced below said limit switch and normally extending into the path of said ram, means for limiting downward pivotal movement of said sensing arm, an elongated counterweight pivotally mounted by one end on said support stand spaced below said sensing arm, a cable rigidly attached by one end to said actuating arm at a point opposed to its counterweighted portion, the opposite end of said cable being attached to said sensing arm at a point re mote from its pivoted end, a fitting having an opening therethrough attached to said counterweight with at least a portion of said opening directed longitudinally of said counterweight, said cable being threaded through said fitting between said actuating arm and said sensing arm, a collar circumferentially fixed on said cable normally abutting the end of said fitting toward said actuating arm and limiting travel of said cable through said fitting in one direction, said sensing arm being adapted to be raised by said ram traveling upwardly to thereby raise said counterweight and remove cable-tension from said counterweighted actuating arm to effect rotation of said actuating arm to interrupt current to said electrically powered ram raising means.

2. The improvement as defined by claim 1 in which said fitting is pivotally mounted on said counterweight.

3. The improvement as defined by claim 1 in which said fitting is in the form of an arcuate tube.

4. The improvement as defined by claim 1 in which said sleeve is fixed on said cable at a point whereby disposition of said sensing arm and said counterweight in substantially parallelogram form is achieved.

5. The improvement as defined by claim 1 in which said means for limiting downward pivotal movement of said sensing arm is vertically adjustable relative to the vertical path of said ram.

6. The improvement as defined by claim 1 in which stops are disposed at opposite ends of the arcuate path of travel of said actuating arm. 

1. In a crane hoist having a ram disposed for movement in a vertical path, electrically powered means for raising said ram, a limit switch connected with said means for controlling the flow of electrical current thereto, an actuating arm connected with said limit switch, said actuating arm being counterweighted to constantly urge said limit switch into current-interrupting position, the improvement therewith of apparatus for controlling the upward movement of said ram through actuation of said limit switch, said apparatus comprising a support stand disposed adjacent the path of said ram, said limit switch being disposed on said support stand, a sensing arm pivotally mounted by one end on said support stand spaced below said limit switch and normally extending into the path of said ram, means for limiting downward pivotal movement of said sensing arm, an elongated counterweight pivotally mounted by one end on said support stand spaced below said sensing arm, a cable rigidly attached by one end to said actuating arm at a point opposed to its counterweighted portion, the opposite end of said cable being attached to said sensing arm at a point remote from its pivoted end, a fitting having an opening therethrough attached to said counterweight with at least a portion of said opening directed longitudinally of said counterweight, said cable being threaded through said fitting between said actuating arm and said sensing arm, a collar circumferentially fixed on said cable normally abutting the end of said fitting toward said actuating arm and limiting travel of said cable through said fitting in one direction, said sensing arm being adapted to be raised by said ram traveling upwardly to thereby raise said counterweight and remove cable-tension from said counterweighted actuating arm to effect rotation of said actuating arm to interrupt current to said electrically powered ram raising means.
 2. The improvement as defined by claim 1 in which said fitting is pivotally mounted on said counterweight.
 3. The improvement as defined by claim 1 in which said fitting is in the form of an arcuate tube.
 4. The improvement as defined by claim 1 in which said sleeve is fixed on said cable at a point whereby disposition of said sensing arm and said counterweight in substantially parallelogram form is achieved.
 5. The improvement as defined by claim 1 in which said means for limiting downward pivotal movement of said sensing arm is vertically adjustable relative to the vertical path of said ram.
 6. The improvement as defined by claim 1 in which stops are disposed at opposite ends of the arcuate path of travel of said actuating arm. 